Observational study over 8-year period evaluating microbiological characteristics and risk factor for isolation of multidrug-resistant organisms (MDRO) in patients with healthcare-associated infections (HAIs) hospitalized in a urology ward

Objective: To analyze, in a urology ward, the prevalence and characteristics of healthcare-associated infections (HAIs) due to multidrug-resistant organisms (MDRO). Methods: We carried out an observational study from 2012 to 2019, evaluating MDRO among patients with HAIs, who were hospitalized in the urology ward. MDRO include Pseudomonas spp., resistant to at least three antibiotic groups, extended-spectrum beta-lactamase (ESBL) producing Enterobacteriaceae or those resistant to carbapenems, and Enterococcus spp. resistant to vancomycin. Results: Among patients with HAIs, MDRO were isolated in 100 out of 438 (22.8%) positive cultures. Univariate and multivariate analyses reported that prior urinary tract infection (UTI) [OR 2.45; 95% CI 1.14–5.36; p=0.021] and immunosuppression [OR 2.13; 95% CI 1.11–4.10; p=0.023] were risk factors for MDRO. A high prevalence of MRDO was found in patients with a catheter in the upper urinary tract; 27.6% for double J stent, 29.6% in those with a nephrostomy tube, and 50% in those with a percutaneous internal/external nephroureteral (PCNU) stent. MDRO were isolated in 28.4% of cultures with Enterobacteriaceae (23.8% and 44.7% in those with E. coli and Klebsiella spp.); 7% of Enterobacteriaceae showed resistance to carbapenems (1.3% and 10% for E. coli and Klebsiella spp., respectively). Three out of 80 Enterococcus spp. were vancomycin-resistant. The rate of Pseudomonas aeruginosa resistant to at least three antibiotic groups was 36.3%. Conclusions: The isolation of MDRO, in up to 25% of positive cultures in a urology ward, constitutes a challenge for the selection of antibiotics. MDRO are more common in immunosuppressed patients, those with previous UTIs, and those with a catheter in the upper urinary tract.


Introduction
The prevalence of multidrug-resistant organisms (MDRO) has been increasing worldwide in recent years [1], [2]. Isolation from MDRO is of utmost importance in patients with healthcare-associated infections (HAIs) [3], [4], [5]. It is a public health warning that, far from being controlled, this seems to be one of the main challenges for medicine in the 21 st century. It is a problem that concerns all physicians and healthcare workers who manage patients with infections and use antibiotics. It is also necessary to bear in mind that when MDRO is isolated, there is limited availability of antibiotics to be prescribed [1], [6]. Thus, it seems of increasing importance for the detection of risk factors for HAIs and the isolation of MDRO to develop specific protocol and stewardship programs. The prevalence of MDRO has been analyzed in some epidemiological studies [7]. However, data on the prevalence of MDRO in patients admitted to a urology service are limited. The main evaluation of MDRO in urology has been carried out by the GPIU study [4], [5], [8]. Urological patients have specific characteristics and specific risk factors, such as urinary catheters and surgery during hospitalization. Therefore, an adequate knowledge of risk factors, microbiological and resistance patterns for isolation of MDRO may allow select appropriate empiric antibiotic therapy and optimize outcomes [9]. Our purpose was to analyze the prevalence and characteristics of HAIs due to MDRO in patients admitted to a urology ward.

Methods
We have carried out an observational study from January 2012 to December 2019, evaluating the prevalence and risk factors for isolation of MDRO in patients with HAIs admitted in a urology ward. The study collected information of all patients admitted in the urology ward from scheduled admission or the emergency department. Pediatric patients and those who underwent kidney transplantation are not included, since they are admitted to the pediatric urology and nephrology departments, respectively. We collected demographic data of all the patients admitted to our department, such as age, gender, comorbidities such as arterial hypertension, diabetes mellitus, cardiovascular disease, liver disease, immunosuppression, and health condition using the American Society of Anesthesiologists' (ASA) score. Regarding urological risk factors, we collected urinary lithiasis, previous urinary tract infection (UTI), a urinary catheter (urethral or in the upper urinary tract, during hospitalization or placed prior to admission). The prevalence of infections was assessed and defined clinically regardless of the results of the cultures. Healthcare-associated infections (HAIs) are defined according to the criteria of the Centers for Disease Control and Prevention as infection diagnosed 48 hours after admission or those with any of the following criteria: received parenteral treatment, specialized wound care, hemodialysis, or intravenous chemotherapy; those admitted to an acute hospitalization ward for at least two days in the last 90 days, or institutionalized in a residence or long-stay center. Multidrug resistance was defined according to the ECDC and CDC definitions of multidrug resistance (MDRO), extensive drug resistance (XDR) and pan-drug resistance (PDR). MDRO was defined as acquired non-susceptibility to at least one agent in three or more antimicrobial categories, XDR was defined as non-susceptibility to at least one agent in all but two or fewer antimicrobial categories (i.e. bacterial isolates remain susceptible to only one or two categories) and PDR was defined as non-susceptibility to all agents in all antimicrobial categories [10]. We use the definition recommended by the ECDC and CDC which includes extended-spectrum beta-lactamase (ESBL) producing Enterobacteriaceae or those resistant to carbapenems, Enterococcus spp. resistant to vancomycin, and Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa resistant to more than three classes of antimicrobial agents. Pathogen identification, antimicrobial susceptibility testing and screening for ESBL and carbapenemase-producing bacteria were performed according to the cut-off point of resistance set by EUCAST (https://www.eucast.org). In brief, specimens were collected and processed following conventional microbiological procedures for correct management of clin-ical samples. Blood agar and MacConkey agar media were used. Identification and susceptibility tests were determined using the MicroScan ® panel. The initial screen test to indicate ESBL production was done using cefotaxime and clavulanic acid. The confirmatory test was carried out by using the double disk synergy method with the determination of the MIC testing ceftriaxone or ceftazidime and ceftriaxone/ceftazidime in combination with clavulanic acid. E-test (Epsilon test) was also performed in those cases in which results were not conclusive. Carbapenemase-producing bacteria was considered to be any enterobacteria in which the values of the minimum inhibitory concentrations of at least one carbapenem (imipenem, meropenem, doripenem, or ertapenem) were equal to or higher than the cut-off point of resistance. The type of carbapenemase-producing bacteria was also reported. The type of HAIs was reported including healthcare-associated urinary tract infections (HAUTIs) or other types of HAIs such as surgical site infection, intraabdominal abscess, and vascular catheter associated infections. We also recorded if MDRO were isolated in blood, urine cultures, or samples from surgical site or abscess. The analysis included microbiological characteristics and risk factors for isolation of MDR microorganisms in urine or blood cultures. As the study was carried out in a period of 8 years, we also review the evolution over time. Data were presented mainly as frequencies expressed as a percentage in categorical variables; for the quantitative variable, data were reported as mean and standard deviation. Risk factors for isolation of MDRO in patients with HAIs were assessed by univariate analysis using Chisquare tests or Fisher's test for categorical variables and Student's t-test for continuous variables. A multivariate analysis was then performed, including those variables with a p<0.1 in the univariate analysis, to find independent risk factors for the development of infection due to MDRO. Data are presented as frequencies, as well as odds ratio (OR) with 95% confidence interval (95% CI). The p<0.05 are considered statistically significant. The data has been collected and analyzed with the Statistical Package for Social Sciences version 23.0 (SPSS Inc., Chicago, IL., USA).

Results
The results indicated that 778 (5.5%) out of 14,224 patients admitted to the urology ward between 2012 and 2019 reported HAIs, with a prevalence that decreases from 7.3% in 2012 to 2.8% in 2019. The evolution of the prevalence of HAIs is shown in Figure 1. No microorganisms were isolated in 28.4% of patients. One microorganism was isolated in 42.9%. Several microorganisms were isolated in 19.7%. No culture was available or the result showed contamination in 9%. In patients with HAIs with positive cultures, the prevalence of MDRO microorganisms was 22.8%, with figures ranging from 15.5% in 2012 and 2016 to 31.1% in 2015. The evolution of the preva- lence of MDRO is shown in Figure 2. HAUTIs were the most common types of HAIs (71.5%), followed by surgical site infections and intraabdominal abscesses, 17    results of the univariate analysis were summarized in Table 1. Apart from arterial hypertension, the previously mentioned factors were confirmed in a multivariable analysis. Urinary lithiasis was also found as a risk factor in the multivariate analysis (

Discussion
One of the main consequences of antibiotics' widespread use is the emergence of microorganisms with resistance to antibiotics. Nowadays, a primary concern for worldwide healthcare systems is the increasing prevalence of antibiotic resistance in HAIs and outpatient settings. Moreover, the emergence of MDRO is a worrisome point, as selecting an appropriate antibiotic treatment is a challenging task [11]. It is estimated that MDRO infections increase hospitalization costs by 10% to 30% [12], [13]. Our data showed that although continuous monitoring and prevention of infections has led to a decrease in the global prevalence of HAI, there is an increasing prevalence of the presence of MDRO. Specifically, 22.8% were positive cultures with the isolation of MDRO, and up to 7% of patients with isolation of Enterobacteriaceae were producers of carbapenemases. Previous data from our center confirms that carbapenemase-producing Enterobacteriaceae infections represented 3.6% of all healthcareassociated infections and 9.7% of those caused by enterobacteria [14]. The outbreak of carbapenemaseproducing bacteria is one of the most worrisome points, as in this case, the correct selection of antibiotics is a challenging task [1], [3], [14]. The situation is especially serious in some Asian countries, such as India and China, with very high rates of carbapenemase-producing MDRO [15], [16]. Nevertheless, identifying risk factors associated with the isolation of MDRO plays a fundamental role and may add in the choice of empirical antimicrobial therapy, especially if we suspect that we are facing an MDRO with resistance to carbapenems [14], [17]. According to our results, we confirm that the presence of immunosuppression, prior UTIs and urinary catheter in the upper urinary tract are risk factors for presenting MDRO infections. Those factors are also related to a higher risk of HAIs [2], [4], [18]. However, we did not identify, among the possible risk factors analyzed, that the presence of diabetes mellitus or high anaesthetic risk (ASA score III-IV) were predisposing factors for the isolation of MDRO. Among urological patients, those with a catheter in the upper urinary tract (ureteral double J stent, nephrostomy tube, or percutaneous internal-external nephrostomy catheter) require special attention and show a high prevalence of infections due to MDRO [19], [20]. The risk of isolation of MDRO is especially high in those with a percutaneous internalexternal nephrostomy catheter, up to 50% in our series. One of the main issues when dealing with MDRO is the prescription of adequate empirical treatment [17], [21]. In our department, for those hospitalized in a urology ward with HAIs and risk factors for MDRO, the empirical treatment is based on carbapenems (the susceptibility rate was 63.8%) or aminoglycosides such as amikacin (the susceptibility rate was 66.3%). Aminoglycosides were the most common empirical treatment in penicillin allergic patients. Hospital antibiotic stewardship programs and a continuous surveillance of infections are recommended in order to optimize the management of infections [22], [23], [24], [25]. Although the prevalence of MDRO is increasing globally, HAIs and MDRO infections must be evaluated locally and revised periodically in each center due to the variability of resistance with essential differences between continents, countries, and even centers in the same region [3], [26]. Therefore, based on clinical practice guidelines, each center has to collect its data on the prevalence of MDRO and design protocols for the prescription of empirical antibiotic therapy [11], [27], [28]. These measures are useful in order to optimize treatments and reduce complications, and will provide a better understanding of the development of resistance [13], [29].
Urologists must be aware that MDRO infections are common, and they are becoming increasingly aware. One of the main activities in urology to assess the characteristics of HAIs is the GPIU study [4], [5]. MDRO infections are a challenging task and may require management with the support of an infectious diseases specialist. However, as urologists manage the patients, they have to involve all diagnostic and therapeutic measures [30].

Conclusions
MDRO are more common in immunosuppressed patients, as well as those with previous UTIs, urinary catheter before admission, and urinary catheters into the upper urinary tract. Therefore, the prevalence of MDRO in urology is a problem of great importance, since up to 25% of the isolates showed MDRO. The evaluation of the prevalence of MDRO is the first step towards developing strategies aimed at better control of HAIs, in addition to knowing the risk factors predisposed to presenting MDRO. This information should be used to determine which antibiotic therapy is the most appropriate. Due to the variability in the prevalence of MDRO infections, multicenter and transnational studies are necessary to develop joint strategies as well as consensus to counteract the progression of resistance to antibiotic therapy.

Note
This article will also be published as a chapter of the Living Handbook "Urogenital Infections and Inflammations" [31].

Acknowledgments
We acknowledge the effort and collaboration of all personnel of the department of urology for preventing infections. Moreover, special thanks to all the residents of our department who have actively collected and reviewed the data.